1. Field of the Invention
The present invention pertains to rotary fluid handling devices, and more particularly to devices such as turboexpanders and compressors. Such a device typically includes a rotor having a series of fluid passageways therethrough, each passageway having one end opening radially outwardly of the rotor. A stator generally surrounds the rotor and supports a number of nozzles communicating with the radial openings of the rotor passageways. Such nozzles are commonly provided on turboexpanders for injecting fluid into the rotor passageways. However, in some cases, such nozzles are also provided in compressor stators to receive fluid from the compressor impeller passageways. In any event, the nozzles may be defined by a number of blades pivotally mounted on the stator. In order to close the axial openings between the blades and also to provide for adjustment of the blade angle, a clamping ring may be provided axially adjacent the blades. This ring is connected to the blades by suitable cam mechanisms, such as pin and slot arrangements, so that, upon rotation of the clamping ring, the angle of the blades will be varied.
In such devices, it is necessary to provide bearing means to support the clamping ring for axial movement and rotation relative to the stator. Also, the radially inner and outer portions of one axial side of the clamping ring may be exposed to different pressure zones of the fluid handling apparatus, and it is desirable to provide a seal between the zones. Finally, it is necessary to provide a means for urging the adjusting ring axially against the nozzle blades with sufficient force to clamp the ring against the blades and thereby close the axial openings therebetween. However, this force should not be so great as to impede the movement of the blades during adjustment.
2. Description of the Prior Art
In prior devices of the type described above, it is customary to form the clamping ring and an adjacent portion of the stator so that they define respective opposed radially facing annular surfaces. Then, a bearing ring may be emplaced between these surfaces to support the clamping ring for axial movement and rotation with respect to the stator. This bearing ring may also serve to seal between radially inner and outer portions of the side of the clamping ring opposite the nozzle blades. Thus, the portion of that side of the clamping ring which is located radially inwardly of the sealing point may be communicated with a zone of the apparatus having a pressure different from that of the zone which communicates with the radially outer portion of that side of the clamping ring.
Accordingly, prior art devices have utilized the pressures of the two aforementioned zones to urge the clamping ring against the nozzle blades, and the position of the sealing point along the radial extent of the clamping ring has been selected to provide a given ratio between the portions of the side of the ring communicated with the high and low pressure zones respectively so as to provide a desired amount of thrust on the clamping ring. However, in practice, it is frequently impossible to precisely predict the seal point location which will result in the proper thrust in a given application. Accordingly, in many instances, it has been found that when the device is placed in operation, too much or too little thrust is imposed on the clamping ring. In such instances, it is necessary to return the device to the manufacturer for modification. This, of course, is relatively expensive and causes undue delay in putting the device to its intended use.